Summary
We proposed a mathematical model that can estimate the apparent longevity of bees using only both the number of adults and capped brood. Seasonal changes in apparent-longevity estimated using field experimental data provide the following interesting findings:
The apparent longevity of mite-free and pesticide-free bee colonies is almost constant after wintering until mid-September, then begins to increase from late September, continues to increase until the end of wintering, reaching a maximum just before the end of wintering, and eventually drops sharply to a low level after the end of wintering. Such normal seasonal changes in apparent longevity were confirmed also in mite-free colonies which ingested sugar syrup (SS) with pesticides and pollen paste (PP) without pesticides. The above results that the apparent longevity of adult bees begins to extend since late September and the fact that worker bees become adult bees on the 21st day after the oviposition of the queen suggest the need to prevent exposure to bee swarms to mites and pesticides from early September as a measure to prevent failure of wintering of bee colonies.
On the other hand, in the mite-free colony which ingested neonicotinoid-containing PP and the mite-infested colonies, the apparent longevities do not exhibit normal seasonal changes and show abnormal seasonal changes, which do not extend and remain almost constant or even shortens since late September as if the bees are unaware of the approach of winter.
Judging from the fact that pollen is the main food of bee brood (larvae and pupa), that mites parasitize the brood, that neonicotinoids remain toxic for a long time, and that the vital functions and organs of honey bees are produced during the larval and pupation periods, it can be inferred that neonicotinoid-containing PP and parasitic mites cause serious damage to the bees’ ability to detect the arrival of winter. Such dysfunction in the brood period probably interferes with extending the apparent longevity of adult bees even as winter approaches.
One Sentence Summary Damages to functions and sensors by neonicotinoid pesticides and mites in larval and pupal period, may erase the increase in bee-longevity during wintering.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Abstract updated to clarify the the explanation of the state and cause of the unusual seasonal change of apparent longevity; Section on Mite-infested colony revised;; Supplementary materials revised; Some corrections were made throughout the text to confusing English phrasing and lexical errors.
